Hydraulic load weighing scale and mounting therefor



United States Patent 72] Inventor Murrel C. Maugh 2537 Wood Ave.,Eugene, Oregon 97402 [21] Appl.No. 761,102 [22] Filed Sept. 20, 1968[45] Patented Dec.8,1970

[54] HYDRAULIC LOAD WEIGI-IING SCALE AND MOUNTING THEREFOR 17 Claims, 8Drawing Figs.

[52] U.S.Cl.., 177/208, 177/141 511 Int.Cl G01g5/04, G01g19/l0 [50]FieldoISearch 177/208, 209,141

[56] References Cited UNITED STATES PATENTS 1,623,414 4/1927 Jensen177/208X 2,652,241 9/1953 Williams. 177/208 2,826,404 3/1958 Stigum177/141 2,867,432 1/1'959 Barkeretal... 177/141 2,960,328 11/1960Tate.... 177/208UX 2,981,101 4/1961 Buck l77/208X Primary ExaminerRobertS. Ward, Jr. Attorney-Oliver D. Olson ABSTRACT: A hydraulic loadweighing scale, comprising upper and lower plates sealed togetherperipherally and containing hydraulic fluid between them, is mountedbetween upper and lower relatively movable members of a vehicle by meansof a universal connecter. The weighing scale is compensated fortemperature variations by the arrangement wherein the maximum thicknessof at least one of the scale plates is established by the ratio TWhereinA is the area of the plate subjected to hydraulic pressure and Kis a constant ranging between 400 and 600, preferably about 450.

PATENTEDBEB 8197B 3545558 SHEET 2 OF 2 Huh MLIPTGB] C.MO ugh BY INVENTORFig 8. @QQM Hgeni HYDRAULIC LOAD WEIGHING SCALE AND MOUNTING THEREFORBACKGROUND OF THE INVENTION This invention relates to hydraulic loadweighing scales of the type disclosed in my US. Reissue Letters Pat. No.24,200 and more particularly to universal means for mounting such scalesbetween spaced relatively movable members of a vehicle, to eliminatestresses on the scales as the vehicle members move relative to eachother and to permit use of scale plates of predetermined thickness tominimize the effect of atmospheric temperature changes on load weightmeasurements.

Prior scales of the type described heretofore have had their platessecured directly to the upper and lower relatively mova ble members of avehicle by such means as studs secured to and projecting from the scaleplates. Relative movement between the vehicle members thus imposesstresses on the plates, through the studs. In some instances thestresses are sufficient to warp the scale plates to an extent whichreduces the accuracy of weight measurements. In other instances thestresses are sufficient to break the studs and thus disconnect thevehicle members from each other. To minimize these problems, the scaleplates have been made quite thick, thereby resulting in furtherinaccuracies of load measurements due to variation in atmospherictemperature.

SUMMARY OF THE INVENTION In its basic concept, the present inventionprovides a universal connecter by which to mount a hydraulic scale ofthe type described between spaced, relatively movable members of avehicle, thereby allowing the scale to be constructed of plates ofminimum thickness.

Another important object of this invention is the provision of ahydraulic load weighing scale and mounting therefor which are ofsimplified construction for economical manufacture, which are capable ofinstallation with speed and facility and which have long service lifewith minimum maintenance and repair.

The foregoing and other objects and advantages of the present inventionwill appear from the following detailed description taken in connectionwith the accompanying drawings of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an end view of a loggingtrailer having associated therewith a cooperating pair of hydraulicscales and mounting means therefor, embodying the features of thisinvention.

FIG. 2 is a fragmentary side elevation, partly in section, of one of thehydraulic load weighing scales and mounting therefor illustrated in FIG.1.

FIG. 3 is a side elevation, the side elevation, partly in section, of amodified form of mounting.

FIG. 4 is a fragmentary side elevation, partly in section, of a stillfurther modified form of scale mounting.

FIG. 5 is a fragmentary vertical section of still another form of scalemounting.

FIG. 6 is a fragmentary vertical section of a still further form ofscale mounting.

FIG. 7 is a side elevation of another form of scale mounting.

FIG. 8 is aside elevation of a still further modified form of scalemounting.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I of thedrawings, there is shown for purposes of illustration a conventionallogging trailer comprising the main structural frame 10 mountingresiliently by springs 12 upon a pair of axles I4 which are supported bywheels 16. A transverse frame 18 is secured upon the main frame andfunctions as a support for the fixed bunk 20 which is mounted thereon inthe manner described in detail hereinafter.

A swinging bunk 22 is mounted rotatably upon the fixed bunk by thecooperating pivot disks 24 and 26. These disks are secured to the fixedbunk and swinging bunk, respectively, and are maintained in propersuperimposed alinement by a kingbolt (not shown) which extends throughthe center of said disks and is secured to the said bunks. Rub pads 28are secured to the fixed and swinging bunks adjacent their respectiveends to form spaced pairs which limit the degree of lateral tipping ofthe swinging bunk with respect to the fixed bunk.

The trailer assembly just described is connected to a truck or trailerby means of the reach 30. Logs may then be supported between theswinging bunks of the trailer and tractor and secured within theconfines of the laterally spaced chocks 32. The foregoing arrangement isof conventional construction well known to those skilled in the art anddoes not form a part of the present invention.

The fixed bunk is mounted upon the transverse frame in spaced relationto the latter by means of a pair of scale assemblies designed generallyby the reference number 34. As best illustrated in FIGS. 2-5, each scaleis constructed of a pair of superimposed plates 36 and 38 securedtogether about their peripheries by such means as welding 40. A threadedinlet opening is provided in the periphery of the plates, communicatingwith the interior space 42 between the plates. A threaded outlet openingalso is provided in the periphery of the plates and is normally closedwith a plug 44 (FIG. 5). The outlet opening serves to bleed air from theconduits and spaces between scale plates, during filling with hydraulicfluid.

A hydraulic conduit 46 is connected at its opposite ends to the inletopenings of the pair of scales. A branch conduit 48 connects the conduitto a fluid pressure-responsive gage 50 of the type described in myearlier patent identified hereinbefore. The scale system requiresprepressurization with hydraulic fluid, in the same manner as fullydescribed in my earlier patent.

As explained hereinbefore, variations in atmospheric temperaturecontribute adversely to the accuracy of load weight measurements. I havediscovered that this effect is minimized by reducing the thickness ofthe scale plates to a minimum, while maintaining sufficient thicknessfor adequate structural strength for a given installation. Thus, thescale plates need to be thicker for applications in which the scale isto weigh heavier loads. However, I have found that the effect oftemperature variations is minimized by relating the thickness of thescale platesto the area of the plates which is subjected to hydraulic AT2=E pressure, by the ratio wherein T is the Plate thicknessesdetermined by the foregoing ratio have.

been found to represent the maximum thickness for that area of platewhich provides sufficient structural strength for the application of thescale while providing minimum load measurement variation over aconsiderable range of variation in atmospheric temperature.

I have also found that, although it is desirable that both scale platesbe of equal thickness, one of the plates may be thicker for a given areathan dictated by the foregoing ratio.

To illustrate the foregoing, if the area of the plate subjected tohydraulic pressure is about 65 square inches, the maximum thickness ofthe plate may be about inch; if the area is about I 12 square inches thethickness may be about one-half inch; if the area is about 250 squareinches the thickness may be about three-quarters inch. For structuralstrength sufficient for use of the scales on vehicles, it is consideredthat the plates should be at least one-quarter inch in thickness. Inaccordance with the foregoing ratio, the operative area of such a plateshould not exceed about 28 square inches.

In order to minimize the stress imposed on the scale plates dueto therelative movement of frame members of a vehicle, the present inventionprovides universal connecter means for mounting the scale between suchrelative movable members. The drawings illustrate various structuralforms of such a connecter.

Referring first to FIGS. 1 and 2, the connecter includes a bottom platemember 52 adapted to be secured to the bottom, relatively movable member18 of a vehicle. This may be done by welding, bolting, or other suitablemeans. In the embodiment illustrated, the plate members provided with aplurality of spaced openings 54 for the reception of securing bolts, theopenings including an inner, hexagonal or other noncircular portion 54adapted to receive the corresponding shaped head of the bolt. The boltsextend downward through registering openings in the vehicle frame memberIll, and receive securing nuts, as will be understood.

Supported freely on the plate member is a disk 56 of rubber or othersuitably resilient material. This is retained in position by means of anannular groove 58 in the disk which receives the upstanding annular ribtill on the plate member. The disk serves as means to transfer loadpressure from the member 13 to the lower plate 38 of the scale pad.

The connecter also includes an upper plate member 62; similarly providedwith spaced bolt openings 64, 64- and annular rib 66. The latter isreceived in an annular groove in the associated resilient disk at: whichfunctions in the manner of disk 56 to transfer load pressure from memberMl to scale plate 36.

Interposed between the resilient disks is a scale pad of the previouslydescribed construction. To prevent relative displacement of the scalepad and resilient disks a plurality of tabs 70 may be provided on thescale plates to project outward therefrom for reception in pocketsprovided in the resilient disks.

The bottom plate member 52 is provided with an upstanding extendingcircular wall 72 within which the resilient disks and scale pad arefreely confined. The upper plate member 62 is provided with a downwardlyprojecting circular wall 7 which telescopes freely over the wall '72 ofthe bottom plate member. The latter wall is provided with a plurality ofcircumferentially spaced, outwardly projecting lugs 76. The wall of theupper plate member is provided with a plurality of correspondinglyspaced offset locking notches 78 adapted to removably receive thelocking lugs, by relative rotation of the top and bottom plate members.

The lugs are smaller in dimension than the associated notches, wherebyto permit a limited degree of relative movement of the top and bottomplate members. This permits sufficient relative movement of the vehicleframe members, as well as deflection of the resilient disks and scaleplates, for proper operation of the scale. Further, this degree ofuniversal movement of interconnected plate members minimizes stresses onthe scale plates, therr by permitting the latter to be made in minimumthickness, ar. described hereinbefore.

Still further, the enclosure of the scale pad with the walled platemembers and with the resilient disks, serves to insulate the scale padand thus further minimize the effects of changes in atmospherictemperature.

In the embodiment illustrated in FIGS. 1 and 2, the inlet conduit 46 andoutlet plug 44 extend freely through openings in the wall 72 of thebottom plate member and registering, circumferentially elongated slotsin the wall 74 of the top plate member. The slots accommodate relativerotational movement of the top plate member during locking andunlocking.

The form of connecter illustrated in FIG. 3 differs from that shown inFIG. 2 in that the circular walls and locking means of FIG. 2 arereplaced by a pair of semicircular collars tit) and 82 provided withvertically spaced flanges 84 These flanges pro ject inward for receptionin annular grooves as provided in the peripheries of the plate members.Outwardly projecting tabs 83 on the adjacent ends of the :ollars haveregistering openings for the removable reception of connecting bolts 91for securing the pair of collars tog :ther. The flanges are spaced apartsufficiently to provide the required degree of relative universalmovement of the plate members, as will be understood. Gpenings in thecollars freely receive therethrough the inlet conduit 46 and outlet plugThe connecter illustrated in FIG. 4 includes a bottom plate member 92having an upstanding circular wall 94. The central portion 92' of thebottom plate member is formed as a segment of a sphere which projectsupward for supporting the central portion of the lower plate of thescale pad and for transferring load pressure from member 18 to scaleplate 3%, The outer portion of the scale plate is supported by anannular resilient ring )5. A resilient disk 98 overlies the upper plate36 of the scale pad and supports the upper plate member TIMI. This platemember is provided with a plurality of spaced openings 102, 102' forsecuring bolts, in the manner previously described, and also is providedwith an annular rib 104 which is received freely in an annular groove inthe resilient disk Q8.

The upper plate member Mill also is provided with a peripheral shoulderI06 which supports an annular resilient ring M3. The ring is interposedbetween the shoulder and the overlying locking ring M0. The latter isprovided with a downwardly projecting circular wall 112 which telescopesfreely over the upper portion of the upstanding wall 94 on the bottomplate member. Locking lugs ill l on the latter wall cooperate withoffset locking slots 116 in the locking ring wall 112, in the manner inthe embodiment illustrated in FIG. 2. A set screw M3 is provided in thelocking ring wall for engagement with the bottom plate wall, to securethe locking ring releasably in locking position.

As in the embodiment previously described, openings are provided in thewall 94 for receiving the inlet conduit 46 and the outlet plug 44.

In the embodiment illustrated in FIG. 5 a circular wall 120 is welded tothe upper scale plate 36. A spherical pressure transfer segment 122 ismounted at the center of the plate 36, as by means of the pivot stud I22. The segment freely supports a post I26 depending from the plate I23which is adapted to be secured to the vehicle frame member 2b, as by thebolts 134). An annular ring 132 is secured to and projects radially fromthe lower end of the post. The ring supports a resilient annular diskI34 which extends between the post Md and wall 129. A cap member 136overlies the disk and has an internally threaded wall 133 which engagesexternal threads on the wall 120. The cap member thus serves to confinethe disk 134 and, if desired, to preload the latter by tightening thecap member.

The bottom scale plate 37 may be secured directly to the underlyingframe member It]. Alternatively, it may be secured by means of aduplicate assembly of the elements described above.

In FIG. 6 the universal connecter is in the form of a ball-insocketassembly. The ball projects upwardly from a pressure transfer post M2which is secured to a central portion of the upper plate 36 of a scalepad. The ball is received in the hollow portion of the socket member144. A keeper ring 146 is secured to the socket member, below the ball,as by means of the securing bolts 148, to prevent separation of the balland socket members, while accommodating a sufficient degree of relativeuniversal movement therebetween. The bolts serve additionally to securethe socket member 144 to the upper vehicle frame member 20.

It will be understood that another ball-and-socket assembly may beinterposed between a bottom plate 33 of the scale pad and the underlyingframe member 18 of the vehicle, if desired.

In FIG. 7 the universal connecter comprises a shaft 150 journaled at itsopposite ends in bearings 152 the bases 154 of which are secured to thebottom frame member 18 of a vehicle. A cross-shaft I56 secured to theshaft 154) and projecting perpendicular thereto, is mounted rotatably ina bearing 158 the base 160 of which is secured, as by welding, to acentral portion of a bottom plate 38 of a scale pad. If desired, asecond universal connecter of this type may be interposed between thetop plate 36 of the scale pad and the overlying top frame member 25) ofthe vehicle.

The embodiment illustrated in FIG. 8 is similar to that of FIG. 7 withthe exception that the shafts 350 and I56 are separate from each otherand each is positioned to interconmeet a different one of the scaleplates and adjacent vehicle frame members. Thus, shaft 162 is secured topressure transfer plate 164 which, in turn, is secured to the centralportion of the upper scale plate 36. The projecting ends of shaft 162receive bearings 166 which are secured to mounting plate 168. This plateis adapted to be secured to the frame member 29, as by the boltsillustrated.

in order to afford a limited degree of lateral movement of the framemember relative to the scale plate 36, rubber bushings 170 may beinterposed between the end bearings i166 and the shoulders formedbetween the central, larger diameter portion of the shaft 162 and thesmaller diameter end portions thereof.

The other shaft 372 is similar to shaft 162 and is secured to plate 174secured to the central portion of the lower scale plate 38. Theprojecting ends of the shaft 172 receive bearings 176 secured to themounting plate 178 adapted to be secured to the lower frame member 18,as by the bolts illustrated. Rubber bushings, similar to bushings 170may be provided if desired.

From the foregoing it will be appreciated that by the present inventionl have overcome two difficulties attending the use of the hydraulicscale disclosed in my earlier patent identified herebefore. By providinga universal connecter by which to mount the scale between relativelymovable frame member of a vehicle, stresses on the scale plates areminimized and accuracy of load weight measurements is correspondinglyimproved. The universal connecter further allows the scale plates to beprovided in minimum thickness, whereby to minimize the effects ofvariations in atmospheric temperature and thus correspondingly toimprove the accuracy of load weight measurements. Certain of theuniversal connecters described herein also provide thermal thermalinsulation for the scale, to still further improve the accuracy of loadweight measurements.

Although the scale and mounting therefor have been described herein inconnection with relatively movable frame members of a vehicle, it willbe understood that the scale may be employed in other environments, suchas a fixed platformtype scale, wherein the problem of stresses due torelative movement of frame members, are inconsequential, but whereinvariations in atmospheric temperature are to be minimized. in suchinstallations the scale described hereinbefore may be utilized withoutthe universal connecters, it being required only that at least one ofthe scale plates have a maximum thickness in accordance with the ratioexplained hereinbefore.

lt will be apparent to those skilled in the art that various changes inthe size, shape, type and number and arrangement of parts describedhereinbefore may be made without departing from the spirit of thisinvention and the scope of the appended claims.

lclaim:

ll. in a hydraulic load weighing scale having upper and lower platessealed together peripherally and containing hydraulic fluid betweenthem, and means for mounting said scale between spaced upper and lowerrelatively movable members, said means comprising universal couplingmeans interconnecting the scale and at least one of the movable members,the improvement comprising a temperature compensation arrangementwherei' the magrn rrnfliickness of at least one of A lie the scaleplates is determined by the ratio a. a pair of connecting members joinedtogether for relative universal movement;

b. means for securing one of said connecting members to one of themovable members; and

c. pressure transfer means operatively engaging one of said connectingmembers with the scale.

The combination of claim iwhere:

a. said one connecting member comprises one element of aball-and-socltet assembly;

b. said other connecting member comprises the other ele ment of theball-and-socket assembly; and

c. said pressure transfer means comprises a post on one element of theball-in-socket assembly secured to the scale plate facing the adjacentmovable member.

6. The combination of claim 4 wherein:

a. said one connecting member comprises a shaft journaled for rotationin bearing means adapted to be secured to one of the movable members;

b. said other connecting members includes a shaft secured perpendicularto the first named shaft for rotation therewith, and journaled inbearing means secured to the adjacent scale plate; and

c. said pressure transfer means comprises the end face of the bearingmeans which journals the second mentioned shaft.

7. The combination of claim l wherein the universal coupling meansincludes:

a. a pair of connecting members joined together for relative universalmovement and supporting the scale between them;

b. means for securing one of said connecting members to the upperrelatively movable member;

0. means for securing the other of said connecting members to the lowerrelatively movable member; and

d. at least one of the connection members including pressure transfermeans engaging the scale plate facing the adjacent movable member.

8. The combination of claim 7 wherein:

a. said connecting members comprise plate members; and

b. lock means releasably interconnects the peripheries of the platemembers for limited relative universal movement of the latter.

9. The combination of claim 7 including resilient bushing meansinterposed between at least one of the shafts and associated bearingmeans for affording limited relative movement therebetween in the axialdirection of the shaft.

10. The combination of claim ll wherein the universal coupling meansincludes:

a. a pair of connecting members joined together for relative universalmovement and supporting the scale between them;

b. means for securing one of said connecting members to the upperrelatively movable member;

c. means for securing the other of said connecting members to the lowerrelatively movable member; and

d. at least one of the connection members including pressure transfermeans engaging the scale plate facing the adjacent movable member.

ill. The combination of claim 10 wherein:

a. said connecting members comprise plate members; and

b. lock means releasably interconnects the peripheries of the platemembers for limited relative universal movement of the latter.

32. The combination of claim 11 wherein the lock means comprisesinterlocking lug and slot means on the pair of plate members.

13. The combination of claim 11 wherein the lock means comprises acollar having spaced flanges confining said plate members freelytherebetween.

E4. The combination of claim 1 wherein said pressure transfer meanscomprises a resilient member interposed between the plate member andadjacent scale plate.

15. The combination of claim M wherein the resilient member comprises arubber pad interposed between the scale plate and adjacent connectingmember.

by the ratio T nwherein T is the thickness of the plate, A is the areaof the plate subjected to hydraulic pressure, and K is a constantranging from about 400 to about 600.

17. The hydraulic load weighing scale of claim 16 wherein K isapproximately 450 and said ratio determines the maximum thickness ofboth of the scale plates.

